Dog Lumps and Bumps: What to Monitor and When to See a Veterinarian

Dog lumps and bumps are common findings, but you cannot reliably identify what a mass is simply by looking at it or feeling whether it is soft, hard, movable or fixed. Some harmless growths and more serious tumours can resemble one another, and non-cancerous conditions such as cysts, inflammation and abscesses can also create noticeable masses. AAHA’s oncology guidelines recommend sampling masses because palpation or appearance alone cannot determine their type or biological behaviour.

The most useful thing an owner can do is record where the lump is, when it appeared and whether its size, shape, texture, colour, mobility, sensitivity, hair covering or discharge changes. New or changing masses should be discussed with a veterinarian, who may recommend a fine-needle aspirate or biopsy to determine what the lump actually contains.

Direct Answer

A lump on or beneath a dog’s skin may represent many different things, including a lipoma, cyst, wart, abscess, inflammatory swelling or tumour. Softness, hardness, colour and mobility cannot reliably distinguish benign from malignant disease. New, growing, painful, bleeding, ulcerated or otherwise changing lumps should be examined, and microscopic sampling may be required for identification.

Why Appearance Alone Cannot Identify a Lump

One of the most important rules with canine skin masses is:

You cannot reliably tell what a lump is just by looking at it or touching it.

AAHA states that the type and potential behaviour of a mass cannot be determined solely by palpation or imaging. Many non-cancerous conditions can also look like tumours.

Merck makes the same distinction: canine skin tumours are extremely diverse, and determining whether a growth is benign or malignant requires veterinary assessment and often laboratory examination of cells or tissue.

That means none of these findings alone proves that a lump is harmless or dangerous:

• soft
• hard
• round
• irregular
• movable
• fixed
• hairless
• coloured
• small
• large

Use those characteristics for tracking, not home diagnosis.

Skin Lump Versus Deeper Lump

Some masses originate within the skin itself. Others sit in the layer beneath it, known as the subcutaneous tissue, while deeper masses may involve muscle or other structures.

A lump under dog skin may feel as though the skin slides over it. Other masses may seem attached to the skin or underlying structures.

Soft-tissue sarcomas, for example, can occur beneath the skin and vary considerably in both firmness and mobility. Some feel soft and movable, while others feel firm and attached.

Feeling where the lump sits is useful information for the veterinarian, but it does not identify its type.

Soft Lump

Owners often assume a soft lump on a dog is a fatty lipoma.

Lipomas commonly are:

• soft
• beneath the skin
• relatively movable
• slow growing

but other masses can feel similar. Cornell specifically recommends additional testing to confirm suspected lipomas and exclude other tumours that may mimic them.

Merck also notes that mast cell tumours can range from soft to firm and may resemble lipomas.

Therefore:

soft does not automatically mean harmless.

Firm Lump

A firm lump provides information about texture but not diagnosis.

Some benign skin growths are firm. Malignant tumours may also be firm, and inflammatory lesions can feel firm as surrounding tissues react.

Cornell describes soft-tissue sarcomas as potentially ranging from softer, movable masses to firmer lesions attached to deeper structures.

Record whether a lump becomes noticeably firmer over time, particularly if other changes occur simultaneously.

Hard Lump

A hard lump on a dog can be concerning to an owner, but hardness alone cannot determine what it is.

Cysts, calcified lesions, some benign growths and various tumours can all feel hard or solid.

Merck notes that some keratin-filled skin cysts contain a hard or solid core, demonstrating why firmness cannot be used as a cancer test.

A hard mass still deserves assessment if it is new, changing or otherwise abnormal.

Movable Versus Fixed Lump

Mobility is another useful feature to document.

A lump may feel:

• freely movable
• slightly movable
• attached to the skin
• attached to deeper tissue

Many uncomplicated lipomas are movable beneath the skin. However, mobility does not prove that a mass is a lipoma.

Likewise, a fixed mass is not automatically cancerous.

Record the finding, but leave interpretation to the veterinary examination and sampling.

Small Versus Large Lump

Size helps with monitoring and treatment planning, but it cannot tell you whether a lump is benign.

Small malignant tumours exist, while benign growths can become quite large.

Merck describes substantial variation in the size and appearance of canine skin tumours, while treatment decisions depend partly on the diagnosed tumour type, location and size.

Do not wait for a suspicious mass to become large before mentioning it to your veterinarian.

New Lump

A newly noticed lump should be added to a body map and discussed with your veterinarian.

Cornell advises that skin and subcutaneous masses can include both benign and malignant conditions and that there is no way to determine a mass with certainty from appearance alone.

Record:

• date first discovered
• precise body location
• length and width
• colour
• texture
• mobility
• photograph

If possible, do this before the first veterinary visit so there is a baseline for comparison.

Long-Standing Lump

A lump that has existed for months or years without an obvious problem may feel reassuring, but age alone does not confirm that it is harmless.

Some benign masses grow slowly. Some tumours can also remain relatively subtle before changing.

Existing masses should continue to be checked for:

• growth
• altered firmness
• colour change
• hair loss
• ulceration
• discharge
• pain

A previously assessed mass that begins changing should be rechecked rather than assumed to remain the same diagnosis.

Rapidly Growing Lump

Growth rate is particularly useful to document.

Cornell notes that soft-tissue sarcomas can range from slow-growing masses to lesions that seem to enlarge rapidly.

VCA also identifies sudden appearance or rapid growth as features that make veterinarians more concerned about some skin lesions and may lead to biopsy.

However:

rapid growth does not automatically mean cancer.

Inflammation, abscesses and allergic swelling can also develop quickly.

A dog lump growing noticeably should nevertheless be evaluated.

Lipomas

Lipomas are benign masses made of fatty tissue and are common in dogs.

Typical simple lipomas are often:

• soft
• round
• slow growing
• beneath the skin
• movable

and frequently occur on the trunk and limbs.

But a veterinarian should confirm the diagnosis.

Cornell explains that fine-needle aspiration may be recommended to confirm a suspected lipoma and rule out other tumours that may feel similar.

Merck specifically warns that lipomas can be difficult to distinguish from other masses, including some malignant tumours, based on gross appearance alone.

Do not label a soft lump a lipoma at home.

Cysts

Dogs can develop several types of skin cysts, including cysts associated with hair follicles.

Some contain keratin and may feel relatively firm. Others may rupture or become inflamed.

Do not squeeze a suspected cyst.

Merck warns that squeezing keratin-filled cysts can release their contents into surrounding tissues, causing substantial inflammation.

Also remember that a bump that looks like a cyst may turn out to be something different once sampled.

Warts and Papillomas

Canine papillomas are growths associated with papillomaviruses and may have a raised or cauliflower-like appearance.

They are particularly recognised in younger dogs, although cutaneous papillomas can occur at other ages.

However, not every wart-like growth is a true papilloma.

Merck notes that many other skin lesions can resemble warts and that definitive identification may require further testing.

A growth that repeatedly bleeds, ulcerates, becomes painful or changes should be assessed.

Abscesses

An abscess is a pocket of infection and pus that can form beneath the skin.

A subcutaneous abscess may:

• develop relatively suddenly
• feel painful
• be firm or softer
• appear red
• become swollen
• rupture
• produce foul-smelling discharge

VCA notes that bite wounds and foreign material are among potential causes of abscesses.

Do not squeeze or puncture a suspected abscess.

Veterinary treatment may require drainage, investigation for foreign material and appropriate infection management.

Insect Bites

Insect bites and stings can sometimes cause temporary raised areas or swelling.

Merck notes that allergic reactions to insect bites may produce small bumps, hives or swelling and that these reactions can develop relatively quickly.

A temporary itchy bump after a known bite is different from a persistent solid mass that remains for weeks.

Contact a veterinarian more promptly if swelling is severe or accompanied by breathing difficulty or significant facial swelling.

Skin Tumours

Skin tumours can be benign or malignant.

Examples include many different cell types, and their appearances overlap considerably. Merck therefore advises that identifying canine skin tumours should be left to a veterinarian.

Mast cell tumours are an important example because they can vary greatly in:

• size
• firmness
• growth rate
• appearance

and some can mimic a lipoma.

This is one reason sampling is far more useful than attempting to create an online “cancerous lump appearance” checklist.

Other Possible Masses

Not every lump is a tumour.

Other possibilities can include:

• inflammatory nodules
• abscesses
• cysts
• fluid-filled pressure lesions
• allergic swellings
• foreign-body reactions
• enlarged structures beneath the skin

For example, hygromas are fluid-filled swellings that can develop over pressure points such as the elbow.

The broad range of possibilities reinforces why a physical examination and, when indicated, microscopic sampling are needed.

Red Lump

Redness generally indicates inflammation or increased blood flow but is not specific to one condition.

Red masses can occur with:

• inflammation
• insect reactions
• infection
• irritated cysts
• tumours
• self-trauma

Papillomas can become inflamed, while abscesses may cause red painful swelling.

Record whether redness is new and whether the dog is licking or scratching the area.

Bleeding Lump

A dog lump bleeding should be examined rather than repeatedly cleaned and ignored.

Bleeding may occur because a mass has:

• been scratched
• been chewed
• become ulcerated
• been traumatised
• developed fragile surface tissue

Papillomas can bleed when traumatised, while several other skin masses may ulcerate or bleed.

Bleeding does not prove cancer, but recurrent or unexplained bleeding is a meaningful change.

Ulcerated Lump

Ulceration means the skin surface over a lesion has broken down.

Both benign and malignant masses can ulcerate. Merck describes ulceration in several canine skin tumour types, while Cornell notes that some soft-tissue sarcomas can develop open wounds.

Ulcerated tissue may also become uncomfortable or secondarily infected.

A lump that develops an open surface should be assessed.

Painful Lump

Pain is another reason to seek veterinary evaluation.

Abscesses are commonly painful, while tumours or other masses can become painful if they:

• ulcerate
• become inflamed
• compress nearby tissue
• interfere with movement

Cornell notes that soft-tissue masses can cause pain when they involve or compress sensitive structures.

Do not repeatedly squeeze a painful lump to test its texture.

Lump Losing Hair

Hair loss over a mass can occur for several reasons.

The skin may be:

• stretched
• inflamed
• irritated
• repeatedly licked
• directly affected by the lesion

Merck describes several skin tumours as potentially hairless, but alopecia alone cannot identify a tumour type.

If the surrounding coat is also thinning or multiple areas are affected, link readers to Pawnium’s Dog Hair-Loss Article.

Lump Changing Colour

Colour changes should be added to the lump tracker.

Record whether the mass becomes:

• darker
• redder
• bruised-looking
• pale
• crusted

Some mast cell tumours, for example, may change appearance because biologically active substances released by the cells can cause local inflammation or bruising.

But colour change is not specific to mast cell disease.

Any noticeable change from the lump’s previous appearance is useful information for the veterinarian.

Measuring a Lump

Measuring a mass makes monitoring more objective.

Merck describes veterinary tumour mapping that records anatomic location, appearance, palpation characteristics and caliper measurements.

At home, owners can keep things simpler.

Record:

1. Length
2. Width
3. Date
4. Body location

Use the same unit each time, preferably millimetres or centimetres.

Do not press hard or manipulate the lump repeatedly just to obtain a measurement.

Taking Consistent Photographs

Photographs can help show whether the visible appearance changes between veterinary visits.

For better comparisons:

1. Photograph from the same general angle.
2. Use similar lighting.
3. Include a ruler beside the mass when safe.
4. Keep the camera approximately the same distance away.
5. Record the date.
6. Take an additional wider image showing where the lump is located.

Do not rely on photographs to identify what the mass is.

Their purpose is to document change.

Creating a Body Map

Dogs can develop more than one mass, particularly as they age.

Number each lump rather than simply writing:

“lump on side.”

For example:

• Lump 1 – left shoulder
• Lump 2 – right chest
• Lump 3 – left hind thigh

Merck describes tumour mapping as a useful clinical approach in which each mass is recorded by location and physical characteristics.

A body map also prevents confusion when one mass changes and several others remain stable.

Why Owners Should Not Squeeze or Cut Lumps

Do not try to determine what a mass contains by:

• squeezing it
• cutting it
• puncturing it
• inserting a needle
• attempting to drain it

Squeezing a cyst can release keratin into surrounding tissues and provoke substantial inflammation.

Trying to drain a lump can also cause:

• bleeding
• contamination
• infection
• pain
• tissue injury

A lump that needs sampling should be sampled using veterinary technique.

Fine-Needle Aspiration Overview

Fine-needle aspiration, often shortened to FNA, is one of the most common first tests used for lumps and bumps.

A veterinarian inserts a small needle into the mass and collects cells for microscopic examination.

AAHA notes that cytology from fine-needle samples can often diagnose lesions such as:

• lipomas
• cysts
• inflammation
• some round-cell tumours

and can help categorise other types of masses.

FNA is useful, but it is not perfect.

Some solid tumours release relatively few cells, meaning an aspirate can occasionally be inconclusive. Cornell specifically notes this problem with some soft-tissue sarcomas.

Biopsy Overview

A biopsy collects tissue rather than just individual cells.

The tissue is sent for histopathology, where the architecture and characteristics of the lesion can be examined.

AAHA explains that biopsy can provide information not available from cytology, including features such as:

• tumour grade
• invasiveness
• mitotic activity
• tissue relationships

and can provide a definitive diagnosis for many accessible masses.

A biopsy may be recommended when:

• FNA is inconclusive
• the lesion is unusual
• tumour grading is required
• the veterinarian needs additional information before treatment

The best test depends on the individual mass.

When Veterinary Assessment Is Needed

Arrange veterinary assessment for a new dog skin lump, especially if it persists or its identity has not previously been confirmed.

Reassessment becomes more important when an existing lump:

• grows
• becomes firmer or softer
• changes colour
• becomes painful
• loses hair
• starts bleeding
• develops discharge
• ulcerates
• interferes with walking or movement
• changes noticeably from its previous baseline

Veterinary oncology guidance recommends sampling masses because appearance and palpation cannot reliably establish diagnosis.

Seek More Prompt Assessment If…

Contact your veterinarian more promptly for:

• rapid enlargement
• repeated or uncontrolled bleeding
• significant pain
• substantial discharge
• sudden major swelling
• an open ulcerated surface
• a mass interfering with breathing, eating, walking or toileting
• signs of illness such as fever, marked lethargy or reduced appetite alongside a painful swelling

An abscess, for example, can develop relatively rapidly, cause pain and sometimes produce fever or draining pus.

Do not wait for a lump to become large before asking what it is.

FAQs

Can you tell if a dog’s lump is cancerous by touching it?

No. Softness, hardness, mobility and shape cannot reliably determine whether a mass is benign or malignant. AAHA recommends microscopic sampling of masses because palpation alone cannot establish their type or behaviour.

Are soft lumps on dogs usually harmless?

Lipomas are often soft and benign, but other masses can feel soft as well. Mast cell tumours and other lesions can sometimes resemble fatty masses, so a soft lump should not automatically be labelled a lipoma.

Should I worry if my dog’s lump is growing?

Growth is an important change to record and discuss with your veterinarian. Both benign and malignant masses can enlarge, so growth alone cannot identify the cause. Rapidly changing lesions generally deserve timely assessment.

Should I squeeze a cyst on my dog?

No. A bump that appears to be a cyst may not actually be one, and squeezing a true keratin-filled cyst can release material into surrounding tissue and trigger marked inflammation.

What is a fine-needle aspirate for a dog lump?

A fine-needle aspirate uses a small needle to collect cells from a mass. The cells are examined microscopically and may help identify lipomas, cysts, inflammation and various tumours. Some masses still require biopsy if cytology is inconclusive.

Does a lump that has been there for years still need checking?

A long-standing lump may have previously been identified as benign, but it should still be monitored for changes in size, texture, colour, pain, hair loss, bleeding or discharge. A mass that begins changing should be reassessed.